Thickness-dependent in situ studies of trap states in pentacene thin film transistors

摘要

In this letter, we present in situ transport measurements of pentacene thin film transistors, particularly investigations of the evolution of mobility, threshold voltage, and hysteresis during the deposition of pentacene with submonolayer precision. We observe both, a strong positive shift of the threshold voltage and a reduction in the hysteresis up to a nominal pentacene film thickness of four monolayers. In addition to previously published volume electron trap states that account for the threshold voltage shift, we suggest that the existence of shallow pentacene trap states located at the free pentacene surface explains the reduction of the hysteresis.